1. Field of the Invention
The present invention relates to a printed circuit board and an electronic component device.
2. Description of the Background Art
Electronic components such as semiconductor devices or the like generate heat by being driven. When the electronic components generate excess heat, the electronic components malfunction in some cases. Thus, a semiconductor device and a printed circuit board that radiate heat of the electronic components have been proposed to prevent such malfunction of the electronic components (see JP 2003-282778 A, for example).
FIG. 12 is a diagram for use in describing a structure of the semiconductor device of JP 2003-282778 A. In the semiconductor device, a semiconductor device substrate (IC board) 92 as an electronic component is mounted on a printed circuit board 911 by using the flip chip mounting technique.
Specifically, a heat radiation joining bump 98a and an electrically connecting bump 98b are formed on one surface of the semiconductor device substrate 92, and a heat radiation joining pad 912a and an electrically connecting pad 912b are  formed on one surface of the printed circuit board 911.
The heat radiation joining pad 98a and the electrically connecting bump 98b of the semiconductor device substrate 92 are connected to the heat radiation joining pad 912a and the electrically connecting pad 912b of the printed circuit board 911, respectively.
In the printed circuit board 911, openings 91h are formed in a region where the heat radiation joining pad 912a is formed. The openings 91h are filled with silver paste 914.
A metal reinforcing board 916 for heat radiation, which is made from aluminum material or the like, is bonded by using an adhesive 915 to the other surface of the printed circuit board 911 to which the semiconductor device substrate 92 is not connected.
When the semiconductor device is driven, the heat that is generated from the semiconductor device substrate 92 is transmitted to the metal reinforcing board 916 for heat radiation through the heat radiation joining bump 98a, the heat radiation joining pad 912a and the silver paste 914, and diffused from the metal reinforcing board 916 for heat radiation.
Here, the inventors prepared the semiconductor device of FIG. 12 and a semiconductor device without the opening 91h in the configuration of FIG. 12, and evaluated the heat radiation performance of each device.
This evaluation was performed by driving the respective  semiconductor device substrates 92 that were provided on the prepared two semiconductor devices, measuring the temperature of the semiconductor device substrates 92 after a predetermined time (about 20 min.), and comparing the values of the measured temperature.
As a result, the measured temperature value of the semiconductor device of FIG. 12 was about two or three degrees lower than the measured temperature value of the semiconductor device without the opening 91h. However, it is desired that the heat radiation from the electronic components that are mounted on the printed circuit board is performed further sufficiently.